Heretofore, there exists various known types of coupler fittings for attaching an electric metal tube (EMT) to an electrical installation such as an electric box or panel or for joining at least two electrical metal tubes in an end-to-end relationship. Such known coupler assemblies include a coupler body to which the electrical metal tubes are rigidly connected to the coupler body, e.g. as disclosed in U.S. Pat. Nos. 268,686; 3,976,314; 4,073,514; 4,091,523. Other known coupler assemblies include a coupler body wherein at least one connected electrical metal tube is permitted to telescope or slide relative to the coupler body or relative to another electrical metal tube fixedly connected to the coupler body, e.g. as disclosed in U.S. Pat. Nos. 5,141,258 and 6,715,803.
With respect to such known sliding or telescoping coupler assemblies, it has been noted that because of the relatively free or sliding relationship between the moveable electrical metal tube relative to the coupler body, the optimal electrical grounding effect therebetween is substantially diminished because of insufficient contact between the complementary surfaces of the movable electrical metal tube and the associated coupler body due to the required tolerance necessary to permit the desired telescoping between the moveable electric tube and the associated coupler body. Thus, the optimum desired amount of the electrical grounding effect therebetween is not achieved.